The annual mathematics competition for high school students, the oldest of the International Science Olympiads (the first IMO was held in Romania in 1959). The problems come from various areas of mathematics, such as are included in math curricula at secondary schools. Their solution requires exceptional mathematical ability and excellent mathematical knowledge on the part of the contestants. The site includes: regulations, future IMOs, past IMOs (including logos, problems, sometimes results), journals and other info, regional and national mathematics competitions, archives and link collections, schools, and mathematics on the web.